Preheat oven to 400 degrees F. Combine the chicken and buttermilk
in a shallow dish. Cover and chill for 15 minutes.
Spray a baking sheet with cooking spray. Put the cereal
in a sealed plastic bag and crush
with a rolling pin
. Transfer the crumbs to a shallow dish. Season the chicken with the salt and a few grinds of pepper. Dip each piece of chicken in the cereal to fully coat and arrange on the baking sheet. Bake until cooked through, about 8 minutes. Leave the chicken on the baking sheet to cool slightly. It will become crispier.
Serve with the mustard sauce.